Blocking-layer cell



Patented Mar. 28,1950

Willem Christiaan van Geel and Adrlanus J acobus Dekker, Eindhoven,Netherlands, assignors, by mesne assignments, to Hartford National Bankand Trust Company, Hartford, Conn., as

trustee No Drawing. Application April 9, 1946, Serial No. 660,862. Inthe Netherlands September 2, 1944 Section 1, Public Law 690, August 8,1946 Patent expires September 2, 1964 9 Claims. (Cl. 175-366) which atleast for part of its thickness is not formed from any of theelectrodes.

It is known-to manufacture selenium rectifier-s in which the blockinglayer, for instance consisting of quartz, magnesium oxide or otheroxides or amorphous selenium, is applied onto the semiconductiveelectrode by vaporisation. The meth- 0d of applying it by vaporisationhas the drawback of insufiicient reproducibility, due to which theelectric properties of the cells may greatly vary.

According to the invention, in blocking-layer cells comprising ablocking layer which, at least for part of its thickness, is notgenetic, the nongenetic part of the blocking layer is appliedelectrochemically. This method of application has the advantage ofhaving the dosing of the applied substance well under control, inaddition, the

layer applied has a very homogeneous character, as a result of which theinvention ermits the manufacture of selenium cells having excellentproperties in a completely reproducible manner.

According to a special embodiment of the invention the blocking layer isobtained by means of electrophoresis. From a colloidal suspension ofselenium in water or in another dispersion may thus be formed, forinstance, very thin, homogeneous compact layers of selenium having, forinstance, a thickness of say 0.1

A thin blocking layer of excellent quality can also be made byelectrolytic reduction of a solution, for instance a solution of aselenium compound, such as selenious acid in water or of seleniumdioxide in an alcohol.

In manufacturing selenium cells the blocking layer is preferably appliedon to the semi-conductive electrode consisting of selenium, followed byapplying the conducting electrode usually con- J. H. De Boer and W. C.van Gee]. The blockin layer may also be applied on to the metalelectrode. With a rectifying cell consisting of a metal plate, forinstance a nickel plate, against which is pressed a semi-conductiveelectrode, for instance of copper iodide, with the interposition of ablocking layer, the blocking layer may, according to the invention, beprecipitated onto the metal. For example, a blocking layer may be formedon the nickel by electrolysis of a 10% aqueous solution of copperformiate, for instance with a current density of 10 ma./cm. in whichcase insulating cuprous oxide is obtained, or by electrolytic reductionof a 5% aqueous solution of pink salt, which presumably yieldsinsulating compounds of bivalent tin.

Example 1 An aluminium plate covered with an adherentcarbon layer isprovided with a semi-conductive" selemum layer by applying on to itmolten sele-' mum having added to it a small quantity of zircomumchloride for raising the conductibllity; after that the selenium istreated with quinoline and finally, as the case may be after theseleniumlayer hasbeen pressed flat, the assembly is heatedfor some timein order to convert the selenium into the crystalline modification. Thesemi-conductive layer obtained is introduced as a cathode into asolution of 25 gms. of selenium dioxide in 250 cm. glycol, followed bypassing through it for 10 minutes a current having a density of 0.3 ma./cmfi, so that the plate is covered with a layer of amorphous selenium.After the electrolysis the plate is rinsed with water and alcohol andthen heated for about 2 minutes at C. to transform= the amorphousselenium into the crystalline mod-' ification. If the plate is coveredover 1 crn. with a metal layer consisting of an alloy of cadmium,bismuth and tin having a low melting point, and a voltage of 2 v. isapplied, the current in the direction of transmission of the cell, theso-called forward current, appears to be 240 ma. A current of 10 ma. inthe opposite direction, the socalled blocking direction, can only beobtained at a counter-voltage of 18.

If the rectifying cell thus obtained is first formed by passing acurrent through it for some time in the blocking direction, the forwardcurrent amounts t0 285 ma. at 2 volts and the counter' voltage to 36volts for 10 ma.

Example 2 Onto a plate covered with a semi-conductive selenium layer,obtained in the manner set out in the first example, is applied aselenium blocking layer from an aqueous colloidal selenium solution byelectrophoresis for-'15 minutes with a current density of 0.3 ma./cm.'.'I'he colloidal selenium solution is obtained by adding to a solutionof,3.5 cm. of hydrazine hydrate in 100 com. of water, heated at 60 0., asolution of 0.5 g. of selenium dioxide in 5 com. water. This solutionhas a negative charge, so that the semi-conductive seleniumplate shouldbe connected as an anode during the electrophoresis. By proceeding afterprecipitation of the selenium layer, similarly to the first example, oneobtains a forward current of 55 ma. at 2 volts and a countervoltage of 8with 10 ma. After formation these amounts are 70 ma. and 16 volts.

e What we claim is:

1. A method of manufacturing a blocking layer cell, which comprises thesteps of electrophoretically depositing a homogeneous selenium blockinglayer on an electrode of said cell, and applying a counter-electrode onsaid blocking layer.

2. A method of manufacturing a blocking layer cell, which comprises thesteps of applying a layer of selenium to a base to form an electrodethereon, treating said selenium layer with quinoline, converting theselenium into the conductin crystalline modification, cathodicallydepositing a layer of selenium from a solution of selenium dioxide mglycol to form a homogeneous layer of amorphous selenium on saidelectrode, converting said amorphous selenium to the crystallinemodification thereof and thereby forming a selenium blocking layer onsaid selenium electrode, and applying a counter-electrode on said secondlayer of selenium.

3. A selenium blocking layer cell comprising a semi-conductive seleniumelectrode, an electrodeposited homogeneous selenium blocking layer onsaid electrode, and a counter-electrode on said blocking layer.

4. A selenium blocking layer cell comprising a semi-conductive seleniumelectrode, an electrophoretically deposited homogeneous seleniumblocking layer on said electrode, and a counterelectrode on saidblocking layer.

5. A selenium blocking layer cell comprising a semi-conductive seleniumelectrode, an electrolytically deposited homogeneous selenium blockinglayer on said electrode, and a counter-electrode on said blocking layer.a 8. In the manufacture of a blocking layer cell having asemi-conductive selenium electrode applied to a metallic base member anda nongenetic blocking layer on-the selenium electrode, 5

said selenium electrode. converting the amorphous selenium tothecrystalline modification thereof to form the non-genetic blockinglayer on the selenium electrode. and applying a metalliccounter-electrode over the blocking layer to form the blocking l yercell. i

7. In the manufacture of a blocking layer cell having a semi-conductiveselenium electrode applied on a metallic base member and a non-geneticblocking layer on the selenium electrode, the steps comprisingelectrophoretically depositing a homogeneous layer of amorphous seleniumon said selenium electrode, converting the amorphous selenium to thecrystalline modification thereof to form the non-genetic blocking layeron the selenium electrode, and applyi g a metallic counter-electrodeover the selenium blocking layer to form the blocking layer cell.

8. A method of manufacturing a blocking layer cell which comprises thesteps of applying a semiconductive layer of selenium on a metallic basemember to form an electrode of the cell thereon. electrochemicallydepositing a homogeneous selenium blocking layer on said electrode, andapplying a counter-electrode on the said blocking ayer. J

9. A method of manufacturing a blocking layer cell which comprises thesteps of applying a semiconductive layer of selenium on a metallic basemember to form an electrode of the cell thereon, electrolyticallydepositing a homogeneous selenium blocking layer on the said electrode,and applying a counter-electrode on the said blockinglayer.

WIILEM CHRISTIAAN van GEEL. ADRIANUB JACOBUS D.

REFERENCES 'crran The following references are of record in. the file ofthis patent:

UNITED s'ra'rns PATENTS Date Great Britain June 7, 1940 OTHER REFERENCESI Chemical Abstracts, vol. 34, 1940, page 2713.

1. A METHOD OF MANUFACTURING A BLOCKING LAYER CELL, WHICH COMPRISES THESTEPS OF ELECTROPHORETICALLY DEPOSITING A HOMOGENEOUS SELENIUM BLOCKINGLAYER ON AN ELECTRODE OF SAID CELL, AND APPLYING A COUNTER-ELECTRODE ONSAID BLOCKING LAYER.